Robert e



Patented May 1, 1923.

UNITED SATES ROBERT E. WILSON, LEON JV. PARSONS, AND STANLEY 1E. OHXSHOLIYI, OF WASHINGTON,

P A l. bl if" DISTRICT OF COLUMBIA.

PROCESS THE PRODUCTION OE AllHALLEAETELMLETAL PERTJIANGANATES.

N0 Drawing". Application filed September To (all to]: am it may concern.

Be it known that we, Romain E. ll insou, LEON Parsons, and STANLEY L. Unis- HoLM, citizens of the United States. and stationed at Vi ashington, District of Columbia, in the ofiicc of the Director the Chemical l/Varfare Service, Research Division, have invented a Process for the llroduction oi Alkali-Earth-l\letal Permanp anates, of which the following is a specification.

The present invention relates to the production oi? alkah earth metal permanga nates and especially the permanganates of calcium and magnesium as these have beenv found to be very ellicient oxidizing agents for certain purposes, more eflicient even. than the permanganates of the allmliearth metals. This superiority is shown in the so-called British soda lime granules.

More specifically, the object of the invention. is the development of a commercial process oiliproducing the alkali-earth metal permanganates, since so tar as We are aware. their manufacture in quantity has never been attempted on a large scale or even on a small. scale, except in Germany, Where they have been produced by a. rather expensive electrolytic process starting with potassium permanganate (Kb [110 We have discovered that calcium or map;- nesium pern'ianganate cannot be prepared directly by ordinary, methods but that indirect methods must be used. e. g... by first forming a. manganate, oxidizing; this, and neutralizing the perinauganic acid so termed With barium, calcium or magnesium hydroxide.

Vi e have investigated very thoroughly the possible methods of making calcium permangana-te and believe that only tour of them are at all workable. These are:

i (1) Preparation of silver permansenate by crystallization from slowly cooled solutions of silver nitrate and potassium or sodium permanganate. Calcium permanganate is then forn'ied metathetically by treatment with calcium chloride.

(2) Selective transference and oxidation electrolysis of sodium or potassium manga note or permanganate and milk of lime or a calcium. salt. I

(3) Electrolysis of term manganese anode into solution of a calcium salt.

(4) Preparation of barium manganate by fusion or wetmethods, conversion to per manganate by oxidation or acidification, metatheses into calcium pern'iangamite by treatment With calcium sulphate or milk at lime.

O'li' these four possible methods, (1.) is not a possible large scale method. on account of its use ot silver; (2) and are electrolytic methods Without a great deal out promise, and are to be considered elsewhere; l) the principal subject of this application.

Three distinct methods for preparing: barium (or strontium) manganate have been here investigated. The first of? these methods involves heating together barium peroxide, hydroxide, or a salt, such as the nitrate or chlorate, witl an oxide of manganese, as manganese dioxide. Considerable WOl'lI has been done upon fusions ot this type, and beautiful green products were obtained, but the most tavorable results obtained gave products containing only FSlO-"o millin the rest oi the product consistinc, of residual M110 Ball and the Bal int), from the thermal decomposition of the mangranate. The thorough n'iiningr of such dry sintering 's is retl'icr :litlicult, but quite necessary; indeed even the fusions should be stirred to give the best results.

The second and more preferable of these methods involves the reaction of similar mimw tures in alow melt-ins; fused medium. such as fused sodium hydroxide, or sodium nitrate at temperatures Well below a red heat. The cooled fused mass is extra ted with Water. the filtrate containing chiefly NaOll or NaNU being; evaporated to dryness, and the fusion medium being; returned to the process. The insoluble residue cou'.. s ot a basic barium manganiunanganate contaiuiiuy 20-32% Baillnfh, together with excess MnO.,. etc. This represents a decided grain over the first, or dry Fusions.

lloth ol? these methods however, in many ways appear less attractive than a. third method, which consists in boiling green leachings containing about 8% 4 tint) and lb-420% NaO'H, With a soluble barium compound, such as the hydroxide or chloride,filtering oil and washing the insoluble barium manganate precipitate and evaporating down the filtrate to returnthe caustic to the process in the green ash (manganate) fusion. Barium manganate precipitates obtained on a small scale in Illij this wet way contained 75% Ba-MnO the remainder appearing to consist of absorbed alkali and alkaline salts and barium carbonate, unless the green liquor has been previously boiled with milk of lime to remove the carbonate almost invariably present. Even in this case the precipitate generally contains some carbonate due to absorption of atmospheric carbon dioxide during manipulation of the alkaline barium mixtures. The use of the barium hydroxide would probably be preferable to that of a salt such as the chloride as no impurities are thus introduced into the caustic filtrate, to prevent its reuse in the green' ash fusion. The preliminary removal of carbonate with Ca(OH) is preferable to using Ba(OH) for this purpose.

Such mixtures during treatment, should not be allowed to evaporate too far, as

oxygen is then evolved, with the formation of a basic manganrmanganate similar to the product mentioned above in connection with the caustic fusions. Thus by evaporating to pasty-dryness, and thoroughly extracting with water, a dark blue green residue is obtained, in place of the smalt blau manganate, which contains only about 40% Ba'MnO To summarize, probably the best method of making BaMnO, is by a preliminary fusion of NaOH and MnO which is bleached, filtered and treated first with Ca(OH) to precipitate CaCO and then with. Ba(OH) to precipitate BaMnO This gives a very high purity B'aMnO with a minimum amount of BaO used. Considering the great saving in the later conversion of this material t permanganate this method is undoubtedly the cheapest.

Barium manganate is an intermediate product in the manufacture of barium, cal ciun'i and magnesium permanganates. Barium manganate, as prepared by either fusion or precipitation methods may be converted into barium permanganate either by direct oxidation, as by the use of chlorine or ozone, or by the action of acids, the lib erated manganic acid acting as its own oxidizing agent, being itself partially reduced to manganese dioxide in consequence. The calcium permanganate may be obtained by metathesis with the somewhat soluble calcium sulphate, or by neutralizing the acid solution of permanganate with milk of lime;

Of these" two, methods, direct oxidation, on the one hand, and indirect oxidation, by acids on the other harid, the former appears to be at. first sight preferable, because of its directness and because none of the product isjused up in the process. Of the available oxidizing agents to oxidize directly man ganate .to permanganate including chlorine, bromine, and ozone, the first ofthese is the most practicable for technical use. Bromine is barred. because of its scarcity and cost. The use of ozone is entirely too expensive. ,lflven electrolytic oxidation methods, relatively much more efiicient than the ozonizing methods, involve much expensive apparatus.

Chlorination is undoubtedly the best and most economical )rocess of converting BaMnO, into Ba(l\ln() for any purpose where the large amount of chloride impurities could be tolerated. The nitric acid process is undoubtedly the next best, and it appears from the data now available that by careful removal of the nitrate formed by crystallization, a product pure enough for certain more special uses may be made. If still greater purity is required recourse must be had to the carbonation or sulphation methods. Each has some advantages. but both have serious disadvantages for practical commercial operation. The final choice between the two would probably depend on local plant conditions. The Ca(i\lnO,,) is made by either of two ways, depending on the process used in oxidizing the BaMnO If Ba (MnO,) is made, the calcium salt is made by metathesis with CaS(),, filtering off the B2180 Owing to the much greater stability of Ba(MnO,)., as compared with Ca(l\ln(),,) all possible purification. filtration and concentration should be done before the final conversion to Ca(.\1tn(),) is made.

\Vhen a solution or a suspension of a manganate is acidified, manganic acid. being very unstable, breaks down into the relatively much more stable permanganic acid and manganese dioxide. Pcrmanganic acid. while relatively much more stable than mauganic acid, is, however. quite unstable except at low concentrations and low temperatures. Any plan of acid treatment involved in permanganate manufacture must Th s reaction is complete and irreversible on account of the insolubility of the products formed, but, asmightbe expected from the slight solubility of both of the reacting substances, carbon dioxide and barium mangan- Ion lllii llo inseam ate, the solubility of the latter being comparable to that of barium sulphate the rate of reaction is practically negligible at ordinary temperatures and very slow even at the boiling temperature. The great advantage of carbonation for converting barium manganate lies in the very pure product to be obtained by this method.

By using sulphuric acid in place or carbon dioxide a soluble reacting); substance is substituted. for a very slightly soluble one and thus the rate of reaction is greatly increased at the corresponding temperatures. Two of the reaction products are as before insoluble. The use of this acid however, produces such. a high hydrogen ion concentration that it is no longer-possible to work above ordinary or room temperatures on account of the spontaneou decomposition of permanganic acid.

This decomposition is appreciable even. at low temperatures.

This reaction is apparently also retarded by the insoluble product barium sulphate which seems to have a mechanical retarding effect upon the yet undissolved manganate, apparently by the formation oi an insoluble coating upon the particles. This increases the amount of decon'iposition by increasing the length of: treatment required for complete conversion and requires the use of excess H In. the. CO process the reaction can be stopped when Ba(l\/In() is obtained ac cording to the equation:

antic-tr s. an anno Theoretically, it would appear that the same result would follow by using H 80 according to the equation QBaSU, -si (M110 ,rMHo piii.

and actually this must be passed thru as an intermediate stage but in order to obtain. complete conversion oi the manganate enough acid must be added to carry the reaction still further to the following stage By adding Ca(OH) to this reaction mix ture, calcium perm aupganate is obtained. This is essentially the equivalent of adding): Cat), in the alternative method, except that the process is carried out in two stages, '1. e, first the steps oi? precipitating the 132180 by the H 80, and then the neutralization of the HMnO, by means of Caitlin it milk of lime is employed for the neutralization. the resulting filtered solution or: calcium permanganate is of course contaminated with calcium sulphate.

In. the case of nitric acid there is again one soluble reacting substance. in this resembling the action oi? sulphuric acid, but with an ad- 3Ba.l\([1'1() +6HNO Ql-llsln( i -[Mi1U +3Ba(N0 +2H U.

The nitric acid has absolutely no direct oxidizing action in this process, its action is solely that of an acid.

It barium hydroxide is used to neutralize ti S the permanganic acid and any excess nitric acid, the resulting solution contain barium nitrate and permanganate. 13y evaporation it is possible to concentrate the relatively more stable barium. permanganate and sepa rate the less soluble ba rium nitrate. If calcium hydroxide is used for this neutralization and the clear filtrate concentrated by evaporation, the least soluble salt barium nitrate first tends to separate out, followed by calcium nitrate until when concentrated to about a 20% Ca(liln0 only about 5% .la(NQ,) remains in solution and a much smaller proportion of Ba(NO,,

As an example of our process the itollowing experiment was carried out. 22 liters oi green liquor made by an ordinary h'aOlP-L-hilnO tusion containing oi sodium manganate and 524L375 of caustic a1 lrali, part of which was in. the term of can bonate, was boiled for 5 hours with at kilograms of hydrated lime to remove the carbonate. The sludge was removed by dc cantation and filtration. and 12 liters of the filtrate containing 3.41% of sodium mans ganate. was boiled with 1 kilogram. of hy drated barium hydroxide for one hour. The solution gradually became purplish but the green color of inan ranate still persisted and. successive treatments with two portions of 1100 grams each of barium hydroxide for one hour each followed. The solution was cooled and filtered. The dried precipitate was a purplish blue color and contained about 1 kilogram of 74% barium manganate.

Fifty grams of? the 74% barium manganate was suspended in one halt liter of water and was treated with four successive portions oi diluted nitric acid ('1 to 10) each portion being slightly in excess oi that theoretically required to produce complete conversion. The reacting mass was kept cool at all times. The final residue was entirely converted without requiring the boiling with sodium carbonate which it was necessary to employ to complete the conversion when carbonic ple, we claim 1. In aprocess of makingzpermanganates,

adding. to. barium mauganate a reagent which reacts therewith to produce perm anganate radical and treating the same with a compoundot an alkali-earth metal and forming the correspondingpermanganate.

2.. In a. process of making permanganates, addingto an alkali-earth metal .manganate a reagent. which reacts therewith to produce permanganate radical and treating the same with a compoundofan alkali earth metal.

3. Inaiprocess of makingpermanganates, adding'toan allaali-earthmetal manganate a reagent which. reacts therewith to produce permanganate. radical and treating the same with acalcium compound.

4. In a process ofmaking permanganates, adding to an alkali-earth metaliinanganatea reagent which reacts therewith to produce permanganate radical and treating same with calcium hydroxide.

5. -In a process of-making pcrmanganates, addingan oxidizing acidto an alkali-earth metal man'ganate and-then. treating the solu-. tioni with; a compound! of an alkali-earth metal.

-. 6. In a process, of.- making permanganates, adding. nitric acid to antalkalieearth metal manganateand. then formingcalcium per- Calcium sulphate manganatc by treating the solution with a calcium compound.

7. In aprocess of making xarmanganatcs. addingnitric acid to barium manganate and then forming calcium permanganate by treating the solution with acalcium compound.

S. In a process of making permanganates, adding nitric acid to barium manganate, then forming calcium permanganate by treating the solution with a calcium compound andmaintaining the solution cool at all times.

9. In the process for the roduction of permanganatesthe steps which consist in formingpermanganic acid and treating the same with an a1kali earth metal compound to produce an alkali-earth metal permanganate.

10. In the process for the production of pcrmanganates the steps which consist in formingperman anic acid and-treating the same with an al ali-earth metal hydroxide.

11. In the process for the production of permanganates thesteps which consist in formingpermanganic acid and treating the same with. calcium hydroxide.

12. The process for the production of permanganates which consists in forming barium manganate. oxidizing part of the same to produce permanganate radical and treating, the same with a compound of an alkali-earth metal and forming the corresponding permanganate.

13. The process for the production of per manganates which consists in forming an alkali-earth metal manganate, oxidizing part of the same to produce permanganate radical and heating the same with a compound of an alkali-earth metal.

ROBERT E. \VILSON LEON I". PARSONS. 

